Allegiant has argued the union hasn't met all the steps that federal law requires before airline employees can strike. The union, though, has argued it was allowed to strike because the company had not obeyed a court order to restore work rules in its pilot-labor contract.

With the union's assurance, the company said it has no reason to expect any disruption to the airline's flights in the meantime.

About 53 percent of Allegiant's employees are represented by unions, which is less than United, American and Southwest but more than Delta.

Allegiant specializes in flying travelers from smaller cities to vacation destinations such as Las Vegas and Phoenix. It touts low base fares but charges for many extras including seat assignments and carry-on bags. It also provides hotel rooms and car rentals.

The airline is tiny compared with industry leaders such as American, Delta and United, but it is profitable. Last year, parent Allegiant Travel Co. earned $86.3 million.

The shares fell 41 cents to close at $168.22 on Friday. They have gained 12 percent in 2015, but are down 16 percent from their March 18 peak, with most of the decline occurring with the possibility of a strike.

The Lehigh-Northampton Airport Authority, which operates Lehigh Valley International Airport, said earlier this year that if there is a strike, Allegiant passengers would have access to flights to Florida and South Carolina with other carriers, but they would not have nonstop flights.

Allegiant passengers would have to take connecting flights on Delta, United or US Airways.